Continuity as a Guide to Possibility

Abstract

I propose a new guide for assessing claims about what is possible. I offer examples of modal claims that are, in a certain intuitive respect, ‘continuous’ with one another. I then put forward a general, defeasible principle of modal continuity that can account for our intuitions about those examples. According to this principle, statements that differ by a mere quantitative term don't normally differ with respect to being possibly true. I offer a precise statement of the principle, and then I consider exceptions in an effort to find a more nuanced continuity principle that is more reliable and still sufficiently general. Next, I offer a possible explanation of why modal continuity tends to hold and why exceptions occur where they do. Although my primary purpose is to introduce a new technique for modal reasoning, I showcase the power of the principle by applying it to a philosophical dispute concerning parts and wholes: the principle, if true, reveals a new cost of the thesis that composition is restricted. Furthermore, I point out examples of other philosophical inquiries (in philosophy of mind, metaphysics, and philosophical cosmology) that may benefit from a principle of modal continuity. The principle gives us a new tool for assessing a wide variety of modal claims.